Fichas
Erosional landforms (2a)
Fichas del conjunto (31)
- 1CORRIESArmchair-shaped hollow
Upland hills/ mountainside
Steep back wall, over-deepened basin and often a lip at the front (solid rock/ morainic deposits) - 2SizeSome only a few hundred metres across but can be over 15km wide
Walcott Corrie Antarctica over 3km back wall - 3Formation:Several interaction processes
- 41Nivation of small hollow on hillside in which snow collects and accumulates year on year
- 52Hollows enlarge and contain more snow > compresses into névé and then glacial ice
Hollow gets bigger due to movement (abrasion)
Plucking creates a steep back wall
Pressure release de-stresses and weakens rock
Abrasion at base of hollow using material from freeze-thaw weathering and plucking - 63At a critical depth the ice acquired a rotational movement under its own weight
Basal slippage = regelation slip, creep and rotational flow
Rotational flow requires meltwater for lubrication - warm-based glacier
Highest rate of erosions at base due to rotational flow and thickness of glacier - 74Bergschrund = large tensional crevasse formed where moving ice splits away from stagnant ice due to rotational movement
Leaves rock face exposed so freeze-thaw can continue
Debris from plucking and weathering above hollow falls into bergschrund > helps to abrade hollow causing it to deepen - 85Thinner ice at the front unable to erode so rapidly so higher lip is left
May also consist of moraine deposited by the ice as it come out if the corrie
Extending flow - ice flows into valley due to steep gradient to velocity increases (thin so less friction) - 96Post-glaciation the Corrie May become filled with a small circular lake = a tarn
- 10ArrêteNarrow, steep-sided ridge found between 2 corries
Steepening of slopes + retreating corries back to back/ alongside
Striding Edge Lake District - 11Pyramidal peak3 or more corries develop around hill or mountain too and back walls retreat
Matterhorn Swiss alps over 1200m high - 12TROUGHSHas a stepped long profile
Steep gradient:
Faster velocity > ice spreads out (thinner) > extending flow > less erosion
Low gradient in rock basin:
Slow velocity > ice builds up > compressing flow > more erosion - 13Formation:Path carved by glaciers in (entire length of U-shaped valley)
- 141Glacial ice moves through pre-existing river valley > erode sides + floor through abrasion and plucking so becomes deeper, wider and straighter
- 152Creates U-shaped valley
Parabolic due to weathering + mass movement > scree slopes lessen angle after glacier retreats
Flat valley floor due to post-glacial alluvium - 163Compressing flow - enhances abrasion
Alternating bands of hard and soft rock > differential rates of erosion > weaker rock eroded to form basins, harder left as rock step
Ribbon lakes may form in basin - 17Size:U-shaped valley width 0.5 to 3km
- 18ROCHE MOUTONNÉEProjections of resistant rock on the floor of glacial troughs
- 19Size:1-5m high
5-20m long - 20Formation:-
- 211Localised pressure melting on up-valley side as advancing ice passes over them
Smoothed and streamlined + often striations due to abrasion - 222Down-valley side pressure reduced - meltwater re-freezes > plucking and steepening
Steep + jagged
Can indicate direction ice moved - 23ELLIPSOIDAL BASINSFormed by ice sheets
- 24Formation:Ice sheet eroded areas
Bands of softer rock led to over-deepening
Meltwater fills dépressions forming lakes as glacier retreats
Weight of ice led to isostatic lowering of the landscape - 25Size:Laurentide ice sheet north America:
Began to form end of last glacial period 14,000 years ago
Master basin holds Hudson Bay
Smaller basins contain the Great Lakes - Lake Superior average depth 147m - 26STRIATIONSScratches made on rock by debris embedded in base of glacier
Parallel to ice flow - 27Formation:As glacier moves through basal slippage (warm-based glacier)
- 28Glacial groovesLarger e.g. Kelleys Island Ohio
Up to 3m deep
For significant grooves rocks carried in glacier hard geology compared to landscape - 29Chatter marksCrescent shaped gauges chipped out of bedrock as glacier drags rock fragments underneath
Perpendicular to flow
Commonly found with striations - 30HANGING VALLEYTributary glaciers left in smaller valleys high above shrunken central glacier surface > after glacier melts
- 31Formation:Smaller tributary glacier less erosive power so differential erosion
Larger main valley erodes quickly cutting valley deeper
When glacier retreats smaller valley left hanging further up > waterfalls may form
Información
- Descripción
- - (Glaciers) Geography Fichas sobre Erosional landforms (2a), creado por Emily H el 04/11/2018.
- Creado por
- Emily H
- Visitas
- 93
- Valoración